It is desirable to include antistatic agents in detergent compositions to reduce the tendency of laundered fabrics to generate or retain static electricity when subjected to machine drying. Quaternary ammonium compounds have been widely used in detergent compositions for this purpose. However, these quaternary ammonium compounds are known to be generally incompatible with anionic surfactants commonly employed in laundering compositions. The anionic surfactants attack and inactivate the expensive cationic quaternary ammonium compounds in the wash-water environment. Techniques known in the art for preserving the antistatic properties of the cationic quaternary ammonium compounds focused on efforts to physically shield them from the hostile environment. For example, see U.S. Pat. No. 3,936,537, issued to Baskerville et al on Feb. 3, 1976, incorporated herein by reference, which discloses prilling of the quaternary ammonium compound with organic dispersion inhibitors; and U.S. Pat. No. 4,141,841, McDanald, issued Feb. 27, 1979, incorporated herein by reference, which discloses the agglomeration of the above-described prill with certain water-soluble neutral or alkaline salts, using organic agglomerating agents. Substitutes for these relatively expensive quaternary ammonium antistatic compounds would be useful.
Inorganic salts have been widely used as builders for detergent compositions to improve detergency levels of soaps and synthetic detergents, at least in part by sequestering calcium and/or magnesium ions in the wash water. It has also been recognized that various inorganic salts can be effective antistatic agents for fabrics. For example, U.S. Pat. No. 3,348,968, Hulbert et al, issued Oct. 24, 1967, teaches the application of aqueous solutions of certain inorganic salts to reduce static electricity in fabrics. However, inorganic salts have not been used in dry granular detergent compositions for antistatic purposes because they readily dissolve and disperse in the wash water and thus fail to deposit or become trapped on the laundered fabrics.
The present invention, by contrast, teaches the formulation of new discrete antistatic particles for use in granular detergent compositions. These antistatic particles deliver through-the-wash static control and are inexpensive compared to quaternary ammonium compounds. They are formed by encapsulating a water-soluble inorganic salt with an organic dispersion inhibitor material.